Distinct element geomechanical modelling of the formation of sinkhole clusters within large-scale karstic depressions
<p>The 2-D distinct element method (DEM) code (PFC2D_V5) is used here to simulate the evolution of subsidence-related karst landforms, such as single and clustered sinkholes, and associated larger-scale depressions. Subsurface material in the DEM model is removed progressively to produce an ar...
Main Authors: | , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2019-07-01
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Series: | Solid Earth |
Online Access: | https://www.solid-earth.net/10/1219/2019/se-10-1219-2019.pdf |
Summary: | <p>The 2-D distinct element method (DEM) code (PFC2D_V5) is
used here to simulate the evolution of subsidence-related karst landforms, such
as single and clustered sinkholes, and associated larger-scale depressions.
Subsurface material in the DEM model is removed progressively to produce an
array of cavities; this simulates a network of subsurface groundwater
conduits growing by chemical/mechanical erosion. The growth of the cavity
array is coupled mechanically to the gravitationally loaded surroundings,
such that cavities can grow also in part by material failure at their
margins, which in the limit can produce individual collapse sinkholes. Two
end-member growth scenarios of the cavity array and their impact on surface
subsidence were examined in the models: (1) cavity growth at the same depth
level and growth rate; (2) cavity growth at progressively deepening levels
with varying growth rates. These growth scenarios are characterised by
differing stress patterns across the cavity array and its overburden, which
are in turn an important factor for the formation of sinkholes and
uvala-like depressions. For growth scenario (1), a stable compression arch
is established around the entire cavity array, hindering sinkhole collapse
into individual cavities and favouring block-wise, relatively even
subsidence across the whole cavity array. In contrast, for growth scenario (2), the stress system is more heterogeneous, such that local stress
concentrations exist around individual cavities, leading to stress
interactions and local wall/overburden fractures. Consequently, sinkhole
collapses occur in individual cavities, which results in uneven,
differential subsidence within a larger-scale depression. Depending on
material properties of the cavity-hosting material and the overburden, the
larger-scale depression forms either by sinkhole coalescence or by
widespread subsidence linked geometrically to the entire cavity array. The
results from models with growth scenario (2) are in close agreement with
surface morphological and subsurface geophysical observations from an
evaporite karst area on the eastern shore of the Dead Sea.</p> |
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ISSN: | 1869-9510 1869-9529 |